A light emitting diode (LED) has many positive attributes such as a relatively long lifespan, relatively low power consumption, a rapid response rate, environmentally friendly characteristics, and the like, as compared to a light source according to the related art, and has been used as an important light source in various products such as illumination devices, back light units and the like. In a light emitting device using such an LED, a technology of using a phosphor for converting light emitted by an LED chip into different wavelengths of light has been widely used. In particular, the demand for the wavelength conversion technology as described above has increased in the areas of white light emitting devices required in various types of illumination devices and in backlight units for display devices.
A white LED device performs color conversion on a portion of light emitted from an ultraviolet (UV) or blue LED chip through a combination of red, green, blue (RGB) or yellow (Y) phosphors, and implements white light by mixing light emitted from the LED chip and light obtained through the color conversion or mixing several wavelengths of light obtained through the color conversion. In order to obtain high efficiency white light, research into improved conversion efficiency in color conversion materials such as phosphors, as well as improvements in LED chip outputs, has been actively conducted.
FIG. 1 is a cross-sectional view of a white LED device according to the related art. With reference to FIG. 1, an LED device 10 includes a package body 11 including a reflective cup therein, an LED chip 15 and a phosphor layer 12. In general, the phosphor layer 12 may be formed of a resin containing a phosphor. A lens or encapsulating resin part 14 is formed on the phosphor layer 12. The LED chip 15 and the phosphor layer 12 are disposed in an inner portion of the reflective cup (using a cup filling scheme). Since the phosphor layer 12 contacts the immediate vicinity of the LED chip 15, color conversion is initially performed by a phosphor of the phosphor layer 12 and emission of light is then induced through the lens or the encapsulating resin 14.
However, a portion of light emitted from the LED chip 15 is not color-converted by the phosphor of the phosphor layer 12, but is reflected or scattered to be re-absorbed by the LED chip 15, thereby causing a considerable amount of light loss. In addition, heat generated by the LED chip 15 is directly transferred to the phosphor layer 12, such that a reduction in color conversion efficiency may occur. Further, in terms of the inner portion of the phosphor layer 12, since light emitted by the phosphor is re-absorbed by a different phosphor, light loss may occur.